P3 : Particle model of matter

What does the particle model of matter state?

Everything is made up of tiny particles

What are the 3 states of matter?

Solid, liquid, gas

Describe the properties of solids (3)

• Strong forces of attraction hold particles together in a fixed regular arrangement

• Particles don’t have much energy so they can only vibrate

• Have high densities

Describe the properties of liquids (4)

• Weaker forces of attraction between particles

• Particles are close together but can move past each other and form irregular arrangements

• Have more energy than solids + move in random directions at low speeds

• Less dense than solids

Describe the properties of gases (4)

• Basically no forces of attraction between particles

• Particles have more energy than solids and liquids

• Particles are free to move + travel in random directions at high speeds

• Have low densities

What is density? (easy definition)

How ‘compact’ a substance is

What is density? (hard definition)

The mass for a given volume

What is the equation for density?

ρ = m/v

Explain how to find the density of a regular solid (cube) (3)

1. Use a top pan balance to measure the mass of the solid

2. Then measure the length, width and height of the solid and times them together to find the volume of the solid

3. Then use m/v to work out the density

Explain how to find the density of an irregular solid (6)

1. Use a top pan balance to measure the mass of the irregular solid

2. Get a displacement can and full it with water until it is level with the pipe

3. Place a measuring cylinder under the pipe

4. Place the object into the displacement can and wait until the displaced water has been transferred into the measuring cylinder

5. The displaced water is equal to the volume of the irregular object

6. Then use m/v to work out density

Explain how to find the density of a liquid (4)

1. Place a measuring cylinder onto a top pan balance and zero the balance (to reset it)

2. Then pour 10ml (10cm³) of liquid into the measuring cylinder

3. Then record the mass of 10ml of liquid

4. Then use m/v to find the density

What is internal energy?

The total kinetic and potential energy of all the particles that make up a system

Is the change of state a physical or chemical change?

Physical

Why do state changes happen?

Because particles gain or lose energy in their bonds

When a state changes what is conserved?

Mass

When a substance is heated what is increased? (2)

• Temperature

• Energy of particles

Solid → Liquid?

Melting

Solid → Gas?

Sublimation

Liquid → Gas?

Boiling or evaporating

Liquid → Solid?

Freezing

Gas → Liquid?

Condensing

What happens to the temperature when a substance changes state + why?

Stays constant because instead of energy being used for increasing temperature, it is now used to break forces of attraction between particles

What is specific latent heat?

The amount of energy needed to change the state of 1kg of substance with no change in temperature

What are the 2 types of specific latent heat?

• Fusion

• Vaporisation

What is the definition of specific latent heat of fusion?

The amount of energy needed to change of 1kg of substance from a solid to a liquid with no change in temperature

What is the definition of specific latent heat of vaporisation?

The amount of energy needed to change 1kg of substance from a liquid to a gas with no change in temperature

What is the equation for specific latent heat?

E = m x L

Explain what is happening at each stage (mention specific latent heat)

• A → B = Temperature increase ∼ Solid

• B → C = Temperature constant ∼ Solid → Liquid (specific latent heat of fusion)

• C → D = Temperature increase ∼ Liquid

• D → E = Temperature constant ∼ Liquid → Gas (specific latent heat of vaporisation

• E → F = Temperature increase ∼ Gas

What is gas pressure caused by?

The particles colliding with the walls of the container (at right angles) apply a force to the walls of a container causing gas pressure

What do particles exert when they collide into something?

A force → pressure

How would an increase in pressure be achieved? (2)

• Increase in number of collisions per second

• Increased number of energy of each collision

At low temperatures what pressure does a gas have + why + what does this lead to?

Low because the particles have less kinetic energy which leads to fewer collisions per second which lowers pressure

At high temperatures what pressure does a gas have + why + what does this lead to?

High because the particles have more kinetic energy which leads to more collisions per second which increases pressure

What happens to pressure of a gas if the temperature increases but the volume is constant + why?

Pressure will increase because the particles will gain more energy which will lead to more successful collisions per second, leading to an increased in pressure

What will happen to the pressure of a gas if the temperature is constant but the volume increases + why?

The pressure will decrease because the volume will increase and the particles will be more spread out, leading to less collisions, and a decrease in pressure

What is the relationship between pressure and volume?

Inversely proportional

(volume increases, pressure decreases)

What is the equation for a fixed mass held at a constant temperature?

pV = constant

What happens when work is done on a gas?

Energy is transferred to the gas particles → increase in the internal energy (kinetic + potential energy) → increase in temperature